A known ice making machine having a plurality of ice-making cells each of which is opened at the bottom and closed at the top is described in U.S. Pat. No. 4,505,130. This ice machine is shown, by way of example, in FIG. 1 and comprises an ice making mold 1, a water tank 11 disposed therebelow, an ice bin 12 disposed close to water tank 11, and an inclined plate 7 positioned intermediate ice making mold 1 and water tank 11 and having a downward gradient towards ice bin 12. Ice making mold 1 has a soup plate-like member 5 having a large number of through-holes with ice making cups 2 engaged in inverted position in the through-holes. Ice making cups 2 define ice making cells closed at the top and opened at the bottom. An evaporator 3 in the form of a heat exchange tube is disposed in heat exchange relation with ice making cups 2. Inclined plate 7 has water spray openings 8 to permit water to be sprayed into the ice making cells 4 from a plurality of spray nozzles 10a of a water spray tube 10 mounted below inclined plate 7 (only one spray nozzle 10a being shown in the drawing). Plate 7 also has water recovery openings 9 to permit recovery into water tank 11 of return water that has been sprayed into the ice making cells but descended unfrozen onto inclined plate 7. Water is supplied to water spray tube 10 by a water circulating pump 11a associated with water tank 11.
In such ice making machine, prior to starting an ice making cycle of operation, a water valve WV provided to a water supply tube 6 is opened for supplying water to a cavity 5b of soup plate-like member 5. The water thus supplied descends onto inclined plate 7 through an opening 5a in the bottom of soup plate-like member 5 to descend further therefrom into water tank 11 through recovery openings 9 of inclined plate 7. When the water in water tank 11 has attained a predetermined level, water valve WV is closed for driving water circulating pump 11a and a refrigerating system including evaporator 3 into operation. This initiates the ice making operation so that ice making cups 2 are cooled by evaporator 3, while the ice making water is sprayed from spray nozzles 10a into the thus cooled ice making cups 2. Thus, an ice cube is grown gradually in each ice making cell 4. The unfrozen water descends onto inclined plate 7 as mentioned hereinabove.
When the ice cube has grown to a predetermined size, such state is sensed by a known ice making sensor, which then causes cessation of the ice making operation and start of the ice harvesting operation. In such ice harvesting operation, water valve WV is again opened to supply water to cavity 5b of soup plate-like member 5, while simultaneously a hot gas valve, not shown, of the refrigerating system is opened for supplying a hot gas into evaporator 3. The result is that ice cubes formed in the ice making cells 4 are heated and melted free from ice making cups 2 and descend onto inclined plate 7 to slide down thereon to be stocked in ice bin 12.
This prior art method of harvesting the ice represents a loss in ice making efficiency due to: (a.) the amount of ice that is melted during the harvesting operation caused by the excess heat provided by both the hot gas in evaporator 3 and the warm water introduced onto soup plate-like member 5, (b) the time it takes to perform the harvest operation—such time not being available to make ice, and (c) the excess heating of evaporator 3—such heat having to be removed from evaporator 3 during the subsequent ice making cycle.
Hence, there is a strong demand for an ice making machine which avoids the aforementioned deficiency and provides an ice making machine whereby the ice formed in ice making cells can be removed quickly and efficiently minimizing excess meltage of the ice, removing the ice more quickly than is possible with a hot gas defrost, and avoiding any excess heating of evaporator or ice making cells.